In the treatment of diseases, injuries or malformations to bone joints, such as those affecting spinal motion segments, and especially those affecting disc tissue, it has long been known to remove some or all of a degenerated, ruptured or otherwise failing disc. In cases involving intervertebral disc tissue that has been removed or is otherwise absent from a spinal motion segment, corrective measures are taken to ensure the proper spacing of the vertebrae formerly separated by the removed disc tissue.
In some instances, the two adjacent vertebrae are fused together using transplanted bone tissue, an artificial fusion component, or other compositions or devices. Spinal fusion procedures, however, have raised concerns in the medical community that the bio-mechanical rigidity of intervertebral fusion may predispose neighboring spinal motion segments to rapid deterioration. More specifically, unlike a natural intervertebral disc, spinal fusion prevents the fused vertebrae from pivoting and rotating with respect to one another. Such lack of mobility tends to increase stresses on adjacent spinal motion segments.
In other instances, intervertebral disc arthroplasty devices have been proposed for preventing the collapse of the intervertebral space between adjacent vertebrae while maintaining a certain range of pivotal and/or rotational motion therebetween. Such devices typically include articular elements positioned between upper and lower plates, which are further attached to respective superior and inferior vertebrae. The articular elements are typically configured to allow the vertebrae to pivot and/or rotate relative to one another. These motion-preserving devices, however, can result in damage from un-constrained movement. Such movement, or lack of stabilization, can exacerbate disc replacement recovery for patients who have spinal deformities such as scoliosis or spondylolisthesis.
In one embodiment, a motion-preserving implant device for insertion between two bones, such as but not limited to vertebrae, is provided. The motion-preserving implant includes a first plate for engaging with a first bone and a second plate for engaging with a second bone. An articulation member is positioned between the two plates and a motion-controlling member attached to one or both of the plates or is positioned between both plates. In some embodiments, the motion-controlling member is configured to constrain, dampen, and/or bumper the relative motion between the two plates.
In another embodiment, a spinal implant for insertion between two vertebral bodies is provided. The spinal implant includes a first plate for engaging with the first vertebral body and a second plate for engaging with the second vertebral body. The spinal implant also includes an articulation member positioned between the two plates and an elastic motion-controlling member attached to one or both of the plates or positioned between the plates. In some embodiments, the articulation member and the motion-controlling member are configured to provide pivotal and rotational movement between the two vertebral bodies. Also in some embodiments, the articulation member is configured to provide rotational and translational movement between the two vertebral bodies.
A method for inserting a motion-preserving implant between two bones is also provided. In one embodiment, the method includes determining a desired shape of the motion-preserving implant and determining a degree of movement for the motion-preserving implant. One or more elastic members are selected according to the determinations of shape and degree of movement, and the one or more elastic members are assembled into the motion-preserving implant. Once assembled, the motion-preserving implant device is inserted between the two bones.
A kit for use in a surgery addressing a joint between two bones is also provided. In one embodiment, the kit includes at least one motion-preserving implant, the motion-preserving implant having at least one recess for receiving at least one elastic member. The kit also includes a plurality of elastic members for use with the motion-preserving implant. The plurality of elastic members are capable of providing a plurality of different configurations of a motion-preserving implant when received therein.